Computer graphics silhouette load management

Abstract

A method of displaying an object in a real-time simulation using silhouette load mangement techniques, whereby a minimal number of polygons is used in the display process. Two-dimensional silhouettes are created by taking snapshots of three-dimensional models at various angles of view. These silhouettes are stored in texture memory. The appropriate silhouette is selected for display depending upon the angle from which that object is viewed. As the angle of view changes, a different silhouette is selected for display. Once a threshold, such as the angle of rotation or the distance from the viewer, has been reached, the three-dimensional model is substituted for the silhouette for display.

What is claimed is: 
     
       1. In a computer system, a method of displaying an object, comprising the steps of: generating a two-dimensional silhouette representation of the object;   generaing a three-dimensional model of the object comprised of a plurality of polygons;   storing the silhouette representation in texture memory;   determining whether a threshold has been met, wherein   if the threshold is met; reading the silhouette representation from the texture memory;   displaying the silhouette representation;     and if the threshold is not exceeded; rendering the three-dimensional model for display.     
     
     
       2. The method of claim 1 further comprising the step of generating a plurality of silhouettes, wherein the silhouettes correspond to different levels of detail. 
     
     
       3. The method of claim 2 further comprising the step of displaying one of the silhouettes in substitution of a three-dimensional model, wherein the silhouette has less polygons that the three-dimensional model. 
     
     
       4. The method of claim 1 further comprising the step of interpolating a new silhouette from two adjacent silhouettes. 
     
     
       5. The method of claim 1, wherein the silhouettes are generated by taking snapshots of a three-dimensional model in different angles of view. 
     
     
       6. The method of claim 1, wherein the threshold corresponds to an axis of rotation. 
     
     
       7. The method of claim 1, wherein the threshold corresponds to a distance of the object from the viewer. 
     
     
       8. The method of claim 1, wherein a coarse silhouette is generated based upon a model at a higher level of detail. 
     
     
       9. An apparatus for displaying an object on a display screen, comprising: a processor for generating a three-dimensional model of the object comprised of a plurality of polygons and for generating a plurality of silhouette representations of the object, wherein the silhouette representations depict the object when viewed at from different angles;   a texture memory coupled to the processor for storing the silhouette representations;   an interface coupled to the texture memory for accessing a first silhouette when the object is displayed in one frame at a first field of view and for accessing a second silhouette when the object is moved and displayed in a second frame at a second field of view;   a threshold detector for detecting when a threshold has been met, wherein if the threshold is met, the three-dimensional model of the object is displayed instead of the silhouette representation.   
     
     
       10. The apparatus of claim 9, wherein the processor generates three-dimensional models corresponding to a plurality of levels of detail and a set of silhouettes are generated corresponding to each level of detail. 
     
     
       11. The apparatus of claim 9 further comprising logic coupled to the processor for interpolating a new silhouette from two adjacent silhouettes. 
     
     
       12. A method of displaying an object in a real-time simulation, comprising the steps of: generating a plurality of silhouettes of the object, wherein the silhouettes represent the object when viewed from different angles;   storing the plurality of silhouettes in a texture map;   specifying which one of the silhouettes correspond to the angle of view that is to be displayed;   retrieving the specified silhouette from memory;   displaying the specified silhouette;   repeating the specifying, retrieving, and displaying steps for a different silhouette when a field of view corresponding to the object changes;   generating a three-dimensional polygon representation of the object;   determining whether to display the object by either the three-dimensional representation or the silhouette, wherein if the silhouette is selected for display.   
     
     
       13. The method of claim 12, wherein the silhouettes are generated comprising the steps of: modeling a three-dimensional model as a plurality of polygons;   taking a first snapshot of the object, wherein a first silhouette is comprised of the first snapshot having less polygons than the model;   rotating the object;   taking a second snapshot after the object is rotated, wherein a second silhouette is comprised of the second snapshot having less polygons than the model.   
     
     
       14. The method of claim 13 further comprising the step of displaying one of the silhouettes and subsequently substituting the silhouette with the three-dimensional model for display. 
     
     
       15. The method of claim 12 further comprising the steps of: generating a plurality of models for a plurality of levels of detail corresponding to the object;   storing the plurality of models in memory;   generating a plurality of sets of silhouettes corresponding to the plurality of models at different levels of detail;   selecting one of the silhouettes for display according to a level of detail.   
     
     
       16. The method of claim 12 further comprising the step of deriving a new silhouette from two nearby silhouettes. 
     
     
       17. The method of claim 12, wherein a coarse silhouette is generated based on a model corresponding to a higher level of detail.